This project is a follow-up of participants in Project TALENT (PT), a longitudinal study of >440,000 U.S. high school students begun in 1960. The initial two-day assessment included high quality measurement of cognitive abilities, academic and occupational interests, family background, health and personality. Follow-up surveys in 1961-1974 assessed young adult educational and occupational outcomes. This nationally representative sample includes about 4900 twins, 1300 siblings of twins, and 36,000 other sets of siblings from the same schools. Despite their great promise, the twin and sibling data are vastly underutilized - twin pair zygosity (identical or fraternal) is unknown and the sibling structure is only now being identified. We will conduct a new follow-up of selected PT participants, chosen to facilitate separation of genetic, family and neighborhood effects. This includes all twins and their siblings plus 2,500 sets of non-twin siblings who attended the same schools. We will obtain information to assign twin zygosity and combine the new and existing data to create the Project Talent Twin and Sibling (PTTS) study -- the first U.S. national registry of twins. The registry and data archive will be important new resources for research on aging. As part of the new data collection, we will assess cognitive abilities, educational attainment and occupational outcomes, enabling us to evaluate alternative hypotheses for the association between higher educational attainment and preserved cognitive abilities in older age. Possible mechanisms include: (i) direct protective effects of higher education; (ii) preserved capacity due to the greater cognitive complexity of occupational and other activities associated with higher education; (iii) indirect effects via higher abilities in youth predicting both higher educational attainment in young adulthood and cognitive abilities in older age; and (iv) a positive correlation of education with older age abilities via background genetic and environmental factors such as SES. Prior studies are unable to resolve these alternatives due to unavailability of early life cognitive measures, inadequate sample sizes, and confounding of socioeconomic, family environmental, and genetic factors. Distinguishing among these alternatives has significant public health implications -- for designing programs to delay cognitive decline in our elders and for informing educational policies for our youth. PTTS will have unique strengths compared to other longitudinal studies, including: representativeness; a novel design that includes twins, siblings of twins, and other sibling pairs from the same communities; available national norms from 1960 PT data; high quality cognitive measures obtained in adolescence and older adulthood; harmonization of measures with other studies of aging; and a 55-year span from adolescence to older adulthood. The PTTS registry and archive provide an unprecedented basis for answering questions involving societal and biological influences on health and psychosocial outcomes across the lifecourse.